1. Field of the Invention
The present invention relates to a device for manipulating a stylet unit, of the type having a stylet sleeve and a stylet located therein, for positioning an electrode cable in a body cavity. In particular, the invention is directed to a device of this type having first and second parts which are movable relative to each other, one of which receives and holds the proximal end of the stylet and the other of which receives and holds the proximal end of the stylet sleeve, and a support and guide structure for a proximal section of the stylet which projects beyond the end of the stylet sleeve when the stylet and stylet sleeve are moved relative to each other.
2. Description of the Prior Art
A device for operating a stylet unit of the above kind for achieving a desired stiffening of an electrode cable during its advancement into a body cavity, e.g. via a vein into the atrium of the heart, and a desired final position for the distal end of the electrode cable by providing the cable with a bent L- or J-like shape is disclosed in U.S. Pat. No. 5,170,787. Here, the distal end of the stylet is pre-bent and is kept retracted inside the stylet sleeve during the electrode cable's insertion phase, giving the distal end of the electrode cable an essentially straight shape, the stylet, in the final positioning of the distal end of the electrode cable, being exposed outside its tubular sleeve to cause the distal end of the electrode cable to assume the desired curved shape. In order to achieve the exposure of the pre-bent distal end of the stylet outside its tubular sleeve, U.S. Pat. No. 5,170,787 proposes a device which either moves the stylet distally in relation to a stationary sleeve or moves the tubular sleeve proximally in relation to a stationary stylet. In principle, the latter option is preferable, since it does not entail any movement of the electrode cable in relation to the stylet unit's operating device. The known operating device comprises two stiff tubes, one telescoping inside the other, in order to obtain a stiffening that prevents the stylet from buckling when its free proximal end is slid distally inside the tubular sleeve respectively when the tubular sleeve is slid proximally over the free proximal end of the stylet in the operating device. This means that the operating device's total linear elongation is relatively large, since the total length of the telescoping tubes must be twice the length of the stylet's stroke in relation to the tubular sleeve.
An operating device for a stylet unit of the initially cited kind is disclosed in European Application 773 036 in which the stiff, telescoping tubes of the operating device according to U.S. Pat. No. 5,170,787 are replaced by a compressible helical spring which supports the free, proximal end of the stylet and which, in turn, is guided with a tight fit in an elongate cavity in a handle housing. In this way the total length of the operating device can be shortened considerably while the number of device parts could be reduced, resulting in lower manufacturing costs for the operating device.